From: Andreas Schwab <schwab@linux-m68k.org>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tuxist <tuxist@tuxist.de>,
Patrick McCarthy <patrickjmc@gmail.com>,
Finn Thain <fthain@telegraphics.com.au>,
Rusty Russell <rusty@rustcorp.com.au>,
Thomas Gleixner <tglx@linutronix.de>,
Darren Hart <dvhart@linux.intel.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Linux-Next <linux-next@vger.kernel.org>
Subject: Re: [BUG -next] "futex: switch to USER_DS for futex test" breaks s390
Date: Fri, 03 Jan 2014 16:41:10 +0100 [thread overview]
Message-ID: <87ppo95azt.fsf@igel.home> (raw)
In-Reply-To: <20140103153651.GB4219@osiris> (Heiko Carstens's message of "Fri, 3 Jan 2014 16:36:51 +0100")
Heiko Carstens <heiko.carstens@de.ibm.com> writes:
> There is also other code that relies on this: e.g. copy_mount_options() my be
> called with KERNEL_DS.
With KERNEL_DS you can *only* access kernel memory, which is unpagable.
If you want to access user memory, you _must_ use USER_DS.
> If DEBUG_PAGEALLOC is turned on, it would crash badly in kernel space
> if it crosses page boundaries and touches an invalid page, even though
> it should survive...
Accessing an invalid page in kernel space is _always_ a bug.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
next prev parent reply other threads:[~2014-01-03 15:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-03 14:19 [BUG -next] "futex: switch to USER_DS for futex test" breaks s390 Heiko Carstens
2014-01-03 14:42 ` Geert Uytterhoeven
2014-01-03 15:36 ` Heiko Carstens
2014-01-03 15:41 ` Andreas Schwab [this message]
2014-01-03 16:09 ` Heiko Carstens
2014-01-07 8:47 ` Heiko Carstens
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